Unintelligent inbreeding as practiced on many a farm, results in run down stock, not so much from inbreeding as from lack of selection. Out-crossing or mixing in of new blood is better than hit-or-miss inbreeding. Intelligent inbreeding is better still. Scientific Theories of Breeding. The main tenet of Darwin's theory of racial inheritance or evolution, was that changes in animal life, wild or domestic, were brought about by the addition of very slight, perhaps imperceptible, variations. He argued that the giraffe with the longest neck could browse on higher leaves in time of drought and hence left offspring with slightly longer necks than the previous generation. Upon this theory the ordinary breeding by selection is based. In case of breeding for show room, the breeder's eye, or the judge's score card, is the tape with which to measure the length of the giraffe's neck. This principle can be applied equally well, even better, to characteristics where accurate measurement may be used. The last forty years of scientific progress has established firmly the general theories of Darwin, but they have also resulted in our questioning his idea that all great changes are due to the sum of small variations. Many instances have been suggested in which the theory of gradual changes could not explain the facts. The theory of mutation, of which Hugo de Vries, of Holland, is the chief expounder, does not antagonize Darwin, but simply gives more weight in the process of evolution to the factor of sudden changes commonly called sports. Let us illustrate: In the giraffe of our former forest, one might appear whose neck was not longer because of slightly longer vertebrae, but who possessed an extra vertebrae. This would be a mutation. In other words, a mutation is a marked variation that may be inherited. We now believe that polled cattle, five-toed Dorkings, top-knotted Houdans, frizzles and black skinned chickens arose through mutations.